Methods For Providing Composite Asperities

ABSTRACT

Novel methods for providing asperities (sometimes referred to as asperates) on interposer contacts. The asperities comprise low electrical resistant particles such as titanium carbide that are bonded or plated in conjunction with nickel or other matrices on metallic substrate pads. An electroplating bath that has the low electrical resistant particles dispersed in solution is used at low current densities to electrolytically plate a composite electrically low resistant abrasive surface. The composite bond between the particles and the substrate can then be further reinforced with a standard metallic electroplate, if desired.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional PatentApplication No. 60/973,511, filed Sep. 19, 2007, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

Integrated circuits are the mainstream products of the semiconductorindustry, and require testing for new designs, reliability andstatistical process quality control. They are the main memory andprocessing devices in computers and all electronic devices that arecurrently found in the home, industry, automobiles and every other walkof life. Integrated circuits can be individually packaged, for examplein a DIP or BGA, or can be combined with other integrated circuits andcomponents into multi-layer circuit panel assemblies. These packages andassemblies are usually mounted on substrates or circuit boards thatprovide mechanical support, and generally require the use of interposersto provide electrical connections and routing within the package orassembly. The interposers are electronic devices that provide asolder-less connection, for example between an integrated circuit and aprinted circuit board.

The interposers connect to electrical contact pads on a surface of amicroelectronic element, such as a circuit panel, a semiconductor chipor other element having a contact bearing surface. The electricalcontact pads, which are made of conductive material, such as copper,aluminum, silver, platinum, tungsten, or nickel, are subject to thebuildup of oxidation or other compounds due to reactions with theenvironment. The oxidation interferes with the ability of theinterposers to form good electrical contact with the electrical contactpads, and thus interferes with the electrical properties of the device.

A technique to overcome this oxidation problem is the use of a sharpabrasive (asperated) surface on the interposer contact points, forexample an array of asperities. The asperities on the interposer areable to penetrate through the buildup of oxides and other contaminantson the electrical contact pads and enable a conductive contact (e.g., ametal-to-metal contact). One method for making such asperities on aninterposer having copper contact points, is to laser-cut into the copperto form a first layer of multiple asperities. The contact points arethen plated in nickel and then gold to form copper/nickel/goldpyramid-like asperities. With the advent of new alloys used in contactpoint creation, however, such laser-cut asperities do not providesuitable penetration over the life requirement of interposers in atesting environment. Another known method is to bond or platesemiconductor particles such as diamond onto a circuit board, so thatthe particles form asperities. This technique provides additionalstructure for the plated material, but if the plated material wearsthrough, the semiconductor particles with their high electricalresistance can cause poor performance or failure in the device.

As technology advances the trend in integrated circuits is smaller andsmaller. The limitations in the known methods for forming asperitiescreates a formidable obstacle in providing an abrasive surface on thecontact pads of interposers. Semiconductor particles do not provideelectrical performance adequate for the high frequency testing oftoday's integrated circuits. The lack of performance in both of theknown approaches described above results in poor long term electricalperformance, and more frequent replacement of interposers in testingenvironments. The down time with attendant loss of productivity inchanging interposers creates a substantial increased cost burden ontesting.

Thus, there is a need to provide improved asperities used in integratedcircuits, which provide improved electrical performance and have anextended useful lifetime.

SUMMARY OF THE INVENTION

The present invention relates to methods for providing asperities on aconductive contact region of a circuit panel, comprising providing acircuit panel having at least one conductive contact region, exposingthe circuit panel to a first electroplating solution comprising a firstconductive metal and a plurality of metal ceramic particles having a lowelectrical resistance, and supplying a low density current to the firstelectroplating solution for a period of time sufficient to co-depositthe first conductive metal and the metal ceramic particles as a firstconductive layer on the surface of the at least one conductive contactregion. Particular methods are those where the first conductive metal isselected from the group consisting of nickel, aluminum, copper, gold,iridium, palladium, platinum, rhodium, ruthenium, silver, titanium, andalloys of these metals, where the metal ceramic particles have anelectrical resistance less than about 10 milliohms, and where the lowdensity current is less than 8 amps per square foot (ASF).

Also provided are methods for providing asperities on a conductivecontact region of a substrate for forming an electrical connection witha contact location on a semiconductor die, comprising providing asubstrate having at least one conductive contact region, exposing the atleast one conductive contact region of the substrate to a firstelectroplating solution comprising a first conductive metal and aplurality of metal ceramic particles having a low electrical resistance,and supplying a low density current to the first electroplating solutionfor a period of time sufficient to co-deposit a layer of the firstconductive metal and the metal ceramic particles as a first conductivelayer on the surface of the at least one conductive contact region,where the first electroplating solution is vigorously agitated duringthe period of time in which the current is supplied. Particular methodsare those where the first conductive metal is selected from the groupconsisting of nickel, silver, copper, gold, and alloys of these metals,where the metal ceramic particles are ceramics of a Group IV metal, aGroup V metal, or a Group VI metal and have an electrical resistanceless than about 25 milliohms, and where the low density current is lessthan 8 amps per square foot.

Further provided are methods for providing asperities on a conductivecontact region of a substrate for forming an electrical connection witha contact location on a semiconductor die, comprising providing asubstrate having at least one conductive contact region, exposing the atleast one conductive contact region of the substrate to a firstelectroplating solution comprising a first conductive metal and aplurality of metal ceramic particles, supplying a low density current tothe first electroplating solution for a period of time sufficient toco-deposit a layer of the first conductive metal and the metal ceramicparticles as a first conductive layer on the surface of the at least oneconductive contact region, where the first electroplating solution isvigorously agitated during the period of time in which the current issupplied, exposing the at least one conductive contact region of thesubstrate to a second electroplating solution comprising the firstconductive metal, and supplying a current to the second electroplatingsolution for a period of time sufficient to induce growth of the firstconductive layer. Particular methods are those where the firstconductive metal is selected from the group consisting of nickel,silver, copper, gold, and alloys of these metals, where the metalceramic particles are ceramics of a Group IV metal, a Group V metal, ora Group VI metal and have an electrical resistance less than about 15milliohms, and where the low density current is less than 5 amps persquare foot (ASF).

Additional advantages and features of the present invention will beapparent from the following detailed description, drawings and examples,which illustrate preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an integrated circuit having an asperated layer formedthereon according to an embodiment of the present invention.

FIG. 2 is a top view of a contact region having an asperated layerformed thereon according to an embodiment of the present invention.

FIG. 3 is a cross-section of the contact region of FIG. 2, according toa first embodiment of the present invention.

FIG. 4 is a cross-section of the contact region of FIG. 2, according toa second embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the presently preferredembodiments of the invention, which, together with the drawings and thefollowing examples, serve to explain the principles of the invention.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the invention, and it is to be understoodthat other embodiments may be utilized, and that structural, chemical,and electrical changes may be made without departing from the spirit andscope of the present invention. Unless otherwise defined, all technicaland scientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. Although any methods and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresent invention, the preferred methods, devices, and materials are nowdescribed.

The present invention concerns methods for providing compositeasperities on the surface of interposers or other electrical contactpads, using low current density electroplating. The asperities compriselow electrical resistance particles such as titanium carbide that arebonded or plated in conjunction with a conductive metal such as nickelonto the interposers or other electrical contact pads. An electroplatingbath that has the low electrical resistant particles dispersed insolution is used at low current densities to electrolytically plate acomposite electrically low resistant abrasive surface. The compositebond between the particles and the substrate may then be furtherreinforced with standard electroplating of the same conductive metal, ifdesired, or with a different conductive metal, or with a layer of thesame metal and a layer of a different metal, such as gold or rhodium.The result of the methods is the formation of an asperated conductivelayer comprising a plurality of asperities, each asperity formed about aparticle core. These asperities are useful to enable interconnections ina variety of devices, such as contactor sockets in load boards, testers,programmers, and other devices, ultra-high frequency sockets, printedcircuit boards, and semiconductor packages. An especially valuable useof the asperities is on interposer contact surfaces.

For example, FIG. 1 depicts a portion of an integrated circuit 10 (notdrawn to scale) with the plated composite asperities according to anembodiment of the present invention. The circuit 10 comprises asubstrate 20 having at least one contact region 30 (two are shown inFIG. 1) comprised of a conductive substance, such as a conductive metal,filled silicone, or the like. In a preferred embodiment, the contactregions 30 are formed from a conductive metal such as aluminum, copper,nickel, platinum, silver or tungsten, preferably copper. In anotherpreferred embodiment, the contact regions 30 are formed from conductivesilicone, for example as described in U.S. Pat. No. 6,734,250. On thesurface of each contact region 30 is an asperated layer 40, which isadapted to make contact with an electrical contact pad or lead 50. Theelectrical contact pad or lead 50 is also formed from a conductivemetal, such as aluminum, copper, nickel, platinum, silver or tungsten,preferably copper.

In a preferred embodiment, the contact regions 30 have a pitch of lessthan 500 μm (19.7 mil), 450 μm, 400 μm, 350 μm, 300 μm, 250 μm, 200 μm,150 μm, 100 μm, 50 μm or 10 μm. The pitch is measured between similarfeatures of adjacent contacts, such as a center-to-center distance. Inanother preferred embodiment, the contact regions 30 have a pitch ofless than 50 μm (1.97 mil), 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15μm, 10 μm, 5 μm or 1 μm, or less than 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.75 μm, 0.5 μm, 0.25 μm, or 0.1 μm, orsmaller pitches. A smaller pitch is desirable for certain applications,because it permits the integrated circuit to accommodate microelectroniccomponents having greater contact densities.

The top view of the asperated layer 40 of an individual contact region30 is shown in FIG. 2, where it can be seen that the asperated layer 40comprises a plurality of asperities 45. The asperities 45 may bearranged randomly as shown in FIG. 2, or may be regularly arranged forexample in a rectilinear grid or array, or in any other regular pattern.The distribution and arrangement of the asperities 45 can be controlledby adjusting the parameters of the deposition methods of the presentembodiments, and through the use of masking layers, as is furtherexplained below. The desired size and the density of the asperities 45formed on any individual contact region 30 will vary depending on thedesign of the integrated circuit, and according to such parameters asthe contact region size and shape, the configuration of the contactregions, the composition of the contact regions, the number of contactregions, the current conducted by the contact regions, and the like.

It is preferred that the asperities have a size substantially smallerthan the size of the contact region, such as less than 1/10th thediameter of the contact region, and more preferably less than 1/15th,1/20th, or 1/30th the diameter of the contact region. In a preferredembodiment, the asperities are less than 100, 90, 80, 70, 60, 50, 40,30, 20, 10 or 5 microns in size, and more preferably less than 85, 80,75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10 or 5 microns insize. In one embodiment, the particles are less than 75 microns in size,preferably less than 45 microns in size. In another preferredembodiment, the asperities are between 5 to 100 microns in size, morepreferably between 10 and 75 microns in size, and even more preferablybetween 45 and 60 microns in size. The asperities may be of a similarsize to each other, for example by carrying out the methods usingparticles having a narrow particle size distribution (e.g., 90% of theparticles are between 45 and 55 microns), or may differ greatly insizes, for example by carrying out the methods using particles having abroad particle size distribution (e.g., 90% of the particles are between5 to 100 microns in size). The desired particle size distribution mayvary for a number of reasons such as the type of connection that isbeing made, the contact region size and shape, the composition of thecontact regions, etc.

Further details of the asperated layer 40 are depicted in FIGS. 3 and 4,which are cross-sectional views of two different embodiments of anexemplary contact region 30 taken along the line A-A in FIG. 2. FIG. 3depicts an embodiment in which the contact region 30 has a plurality ofasperities 45 embedded within a first conductive layer 42. FIG. 4depicts a different embodiment, in which the asperated layer 40comprises a second conductive layer 44 on top of the first conductivelayer 42 in which the asperities 45 are embedded. The composition of thefirst and second conductive layers 42, 44 may be any suitable conductivesubstance that can be electroplated according to the embodiments of thepresent invention. It should be noted that while the asperities 45 aredepicted with generally polygonal shapes and equal sizes in theseFigures, the asperities are by no means limited to regular shapes orsizes, and they may be irregularly shaped and of varying sizes,diameters and heights. For example, the particles forming the asperitiesmay aggregate to form column-like asperities that are taller than theheight of a single particle.

The composition of the asperities may be any suitable low electricalresistance substance having a small particle size, high hardness andtensile strength, compatibility with plating conditions, and electricalconductivity. The necessary hardness of the particles is best understoodby considering that they must be hard enough to penetrate the oxides andcontaminants on the surface of electrical contact pad or lead 50,without significant wear or flattening over time. Preferably, theparticles are also very sharp but less brittle than diamond. The edgesof the asperities should be 1 mil (0.0254 mm) or less in thickness.

The asperated layers are provided by low current density electroplatingmethods, in which the low electrical resistance particles and the firstconductive metal are co-deposited on the surface of the contact region30 to produce a composite asperated layer 40. To achieve thisco-deposition, the low electrical resistance particles are mixed with aplating solution containing the first conductive metal, and as currentis passed through the plating solution, the particles become embeddedthroughout a matrix of the first conductive metal as the metal is platedonto the contact regions 30. The co-deposited particles lodged at ornear the plated surface provide the surface with hard edges to cutthrough the oxides and contaminants on the electrical contact pad orlead 50, allowing the first conductive layer 42 to make electricalcontact with the metal of the electrical contact pad or lead 50. Theparticles forming the asperities are also electrically conductive, andtherefore do not interfere with the electrical connection between thecontact region 30 and the electrical contact pad or lead 50.

The device to be plated, which may be an integrated circuit,semiconductor substrate, or interposer flex panel, can be prepared forplating by overlaying areas not to be plated with a protective layer,for example a photoresist or protective masking layer, so that only thecontact regions 30 are exposed. Either one or both sides of the devicemay be plated at the same time, for example in an interposer flex panelthat interconnects on both sides of the panel, plating on both sides maybe desired in order to provide all contact regions with an asperatedlayer. If desired, the exposed surface of the contact regions 30, e.g.,the contact pads of individual interposers, may be laser etched toroughen the surface of the contact regions. Such roughening results in amore even particle distribution, because the roughening creates highcurrent density points that increase the attraction of conductiveparticles to the roughened areas during electroplating. The rougheningof specific areas can thus be used to create particular geometries orpatterns of asperities, for example rectilinear arrays, spirals,pinwheels, circular patterns and the like, or can be used to create arandom pattern as desired.

The circuit or substrate is placed or suspended in a firstelectroplating solution contained in an electroplating bath. The devicemay be oriented in any desired orientation in the bath, and may varyfrom vertical to horizontal and otherwise depending on the dispersedparticle concentration and the number of asperities desired in theasperated layer. The bath is also connected to a rectifier whichsupplies the current for the electroplating process, so that the chargedifferential between the cathode (the device) and the anode (thesolution) results in plating the particles and the first conductivemetal onto the contact regions.

Typically, low electrical resistance particles are not soluble inelectroplating solutions. The particles are rendered soluble in thepresent solutions by vigorous agitation, which mechanically dispersesthe particles throughout the solution. In order to accomplish this, thebath is provided with means for agitating the electroplating solution,such as by a slurry pump, air agitation equipment (e.g., turbine blowerunit, water washed air unit, etc.), paddle or impeller systems (e.g., areciprocating paddle system), vibratory agitator (e.g., vibromixer), gassparging, ultrasonic agitating equipment, a device to move the cathodeduring plating (e.g., an oscillator attached to the work bar), and thelike. In a preferred embodiment, the means for agitating is a slurrypump or air agitation equipment. In a preferred embodiment, vigorousagitation, e.g., an agitation rate of 0.5 to 5 meters per second, isused.

The first electroplating solution comprises a first conductive metal,which is used to deposit the first conductive layer, and the lowelectrical resistance particles. In a preferred embodiment, the firstconductive metal is a conductive metal such as nickel, aluminum, copper,gold, iridium, palladium, platinum, rhodium, ruthenium, silver,titanium, or alloys or combinations of one or more of these metals. Inanother preferred embodiment, the first conductive metal is nickel,silver, copper or gold or an alloy of one or more of these metals, andin a more preferred embodiment, the first conductive layer is nickel orcopper, or an alloy of one or both of these metals. For example, nickelmay be alloyed with one or more metals such as aluminum, chromium,copper, iron, molybdenum, niobium, tantalum, titanium or tungsten.

The low electrical resistance particles are particles having thenecessary characteristics suitable for use to form asperities andco-deposit with the conductive metal, and can include nitrides, borides,silicides and carbides, as well as iron, steel, and carbon (e.g.,graphite, etc.). In a preferred embodiment, the particles are metalceramics, e.g., a metal boride, borocarbide, boronitride, borosilicide,carbide, carbonitride, carbosilicide, nitride, nitrosilicide, orsilicide, wherein the metal is preferably a Group IV metal (titanium,zirconium, or hafnium), a Group V metal (vanadium, niobium, ortantalum), or a Group VI metal (chromium, molybdenum, or tungsten). In apreferred embodiment, the particles are a Group IV metal ceramic, wherethe ceramic is of a type selected from the group consisting of boride,borocarbide, boronitride, borosilicide, carbide, carbonitride,carbosilicide, nitride, nitrosilicide, and silicide, and in a morepreferred embodiment, the particles are a Group IV or Group V metalcarbide, such as titanium carbide, vanadium carbide, and hafniumcarbide. In another embodiment, the particles are calcium boride.

The particles may comprise a mixture of suitable particles, for examplea mixture of titanium carbide and calcium boride particles. Theseparticles are generally commercially available, e.g., from commercialsuppliers such as American Elements, Inc. (Los Angeles, Calif.) andFujimi Corporation (Elmhurst, Ill.) even in very small sizes, such thatparticle size is not a limiting factor in forming an asperated layereven on the smallest contact regions. Regardless of their composition,the particles must have a low electrical resistance, i.e., an electricalresistance less than about 100 milliohms, preferably less than 50, 40,30, 20, 10 or 5 milliohms, and more preferably less than 10, 9, 8, 7, 6,5, 4, 3, 2 or 1 milliohms. In a preferred embodiment, the electricalresistance of the particles is less than about 25 milliohms, morepreferably less than about 15 milliohms, and even more preferably lessthan about 10 or about 5 milliohms.

The first conductive metal may be mixed with a suitable startingsolution, and supplemented with desirable additives such as surfactants,levelers, buffers, brighteners, grain refiners, wetting agents, and thelike, as is known to those skilled in the art. Starting solutions forplating various metals are well known in the art. For example, if thefirst conductive metal is nickel, a nickel sulfamate solution may beused, or if copper, a copper cyanide solution may be used. Commerciallyavailable electroplating solutions may also be used, for example fornickel, the Barrett Sulfamate Nickel Plating solution sold by MacDermidInc. (Waterbury, Conn.) or the Techni Nickel S or High-Speed NickelSulfamate FFP solutions sold by Technic Inc. (Cranston, R.I.); forcopper, the Techni FB Bright Acid Copper or Technic CU-330 solutionssold by Technic Inc.; for gold, the Technispeed G or Techni Gold 25 ESsolutions sold by Technic Inc.; for platinum, the Platinum TP solutionsold by Technic Inc.; and for silver, the Techni Cyless Silver IIsolution sold by Technic Inc.

In a preferred embodiment, a nickel sulfamate bath is used to deposit afirst conductive layer of nickel. A low stress nickel sulfamate bathsuitable for use in the present embodiments comprises the following:

Ingredient Amount per L Nickel sulfamate 327.6 g Equivalent nickel metal76.3 g Boric acid 29.9 g Dissolution agent (e.g., Barrett Additive “A”or “B”) 2.99 g Wetting/anti-pitting agent (e.g., Barrett SNAP A/M) 2.2 gWater (e.g., ultra pure water) BalanceBarrett Additive “A” is a chloride-bearing corrosion acid and Additive“B” is a bromide bearing acid, both of which are useful to assist indissolving the anode in the bath. These Additives, as well as BarrettSNAP A/M, which is a low foaming anti-pitting and wetting (surfactant)agent that lowers surface tension and allows the plating solution tospread uniformly over the device being plated, are available fromMacDermid Inc. SNAP A/M is designed for use with either air ormechanical agitation. Boric acid acts to increase conductivity and as abuffer in the solution. If the electroplating process is run at atemperature above 32° C., the amount of boric acid used per liter mustbe increased, for example at 32° C. about 31.7 g should be used, at 43°C. about 37.5 g should be used, at 49° C. about 44.9 g should be used,at 54° C. about 46.8 g should be used, and at 60° C. about 48.6 g shouldbe used.

The low electrical resistance particles are added to the solution, in anamount suitable for the desired density of asperities plated onto thecontact regions. Generally, the amount of particles added is within therange of 1 to 250 grams per liter of plating solution, although thisamount will vary depending on the composition of the particles, thecomposition of the bath, the desired density of the asperities, and thelike. For example, in a solution such as the nickel sulfamate bathspecified above, about 10 to 100 grams per liter of titanium carbideparticles can be used to achieve an appropriate asperity density forplating the contact pads of an interposer flex panel, but the amount maybe as low as 2.5 to 7 grams per liter. Other particles may be used inlarger or smaller amounts, for example it may be desirable to useanywhere from 1 to 50 grams per liter of particles, depending on theparticle composition and the desired plating density. In a preferredembodiment, the amount of low electrical resistance particles added toeach liter of the electroplating solution is about 1 to 250 grams, about2 to 225 grams, about 3 to 200 grams, about 4 to 175 grams, or about 5to 150 grams.

Once the electroplating bath has been prepared, the rectifier is used tosupply a low density current to the electroplating solution for a periodof time sufficient to deposit a layer of the conductive metal and thelow electrical resistance particles on the plurality of conductivecontact regions. The current density is supplied within the range of0.01 to 10 Amps per square foot (ASF), which is low density and producesa very uniform plating. Although prior electroplating methods usingdiamond or silicon particles have required 10 to 25 ASF to achieve asatisfactory particle density when co-plated with metal, it hassurprisingly been found that the present combination of low electricalresistance particles and high levels of agitation in the electroplatingbath allows the usage of low current densities to produce satisfactoryparticle density and grain size in the plated asperated layer.Previously it had been thought that such low current densities wouldresult in unacceptable plating results, for example an unsatisfactorilylarge grain size.

In a preferred embodiment, the low current density is within the rangeof 0.05 to 8 ASF, preferably 0.1 to 5 ASF, more preferably within therange of 0.5 to 3 ASF, and even more preferably within the range of 0.8to 2 ASF. In another embodiment, the low current density is less than 8,7, 6, 5, 4, 3, 2, 1, or 0.1 ASF, preferably less than 10, 9.5, 9, 8.5,8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.5, 0.25, or0.01 ASF, and more preferably is less than 2.75, 2.5, 2.25, 2, 1.75,1.5, 1.25, 1, 0.75, 0.5, 0.25, or 0.01 ASF. The amount of time requiredto plate the asperated layer varies according to the size of the lowelectrical resistance particles, the size of the contact regions, thedesired thickness of the asperated layer, and the like. Generally, forthe formation of an asperated interposer layer, the time varies between1 and 30 minutes, more typically between 2 and 20 minutes. Thetemperature of the bath during the plating process may be at roomtemperature (˜20° C.) or at an elevated temperature, for example atemperature between about 20° C. and 80° C., more preferably from about30° C. to 70° C., and even more preferably between about 40° C. to 60°C.

If desired, the asperated layer may be further reinforced (e.g., madethicker) by placing or suspending the device in a conventional metallicelectroplating bath containing a solution of the first conductive metal,and running the plating process at a low current density for anadditional period of time as needed to produce the desired thickness forthe asperated layer, for example between 5 and 25 minutes, and morepreferably between 10 and 20 minutes. The conventional electroplatingbath is preferably of the same type as the first electroplating bath,for example, if a low stress nickel sulfamate bath is used to co-depositthe particles and the first conductive metal, then the conventional bathis preferably also a nickel sulfamate bath.

In those embodiments in which a second conductive layer is desired to bedeposited on top of the first conductive layer, a second electroplatingsolution is used, which comprises a second conductive metal used todeposit the second conductive layer. In a preferred embodiment, thesecond conductive layer is also a conductive metal, which may beselected from the same metals as the first conductive layer, e.g.,nickel, aluminum, copper, gold, iridium, palladium, platinum, rhodium,ruthenium, silver, titanium, or an alloy of one or more of these metals.In another preferred embodiment, the second conductive layer is aconductive noble metal selected from the group consisting of gold,iridium, osmium, palladium, platinum, rhodium, ruthenium, silver, andalloys and combinations thereof. In a particularly preferred embodiment,the second conductive layer is gold or rhodium, or an alloy of one orboth of these metals. To plate the second conductive layer, the deviceis placed or suspended in a second electroplating bath which comprises asecond electroplating solution comprising the second conductive metal.For example, the device is placed in a rhodium plating bath, and currentis applied to plate a layer of rhodium to the desired thickness, e.g., acurrent density of about 2 to 30 ASF is used to plate the rhodium to athickness of about 0.25 to 4.0 microns.

All publications and patents mentioned in the above specification areherein incorporated by reference. The above description, drawings andexamples are only illustrative of preferred embodiments which achievethe objects, features and advantages of the present invention. It is notintended that the present invention be limited to the illustrativeembodiments. Any modification of the present invention which comeswithin the spirit and scope of the following claims should be consideredpart of the present invention.

1. A method for providing asperities on a conductive contact region of acircuit panel, comprising: providing a circuit panel having at least oneconductive contact region; exposing the circuit panel to a firstelectroplating solution comprising a first conductive metal and aplurality of metal ceramic particles, wherein the first conductive metalis selected from the group consisting of nickel, aluminum, copper, gold,iridium, palladium, platinum, rhodium, ruthenium, silver, titanium, andalloys of these metals, and wherein the metal ceramic particles have anelectrical resistance less than about 10 milliohms; and supplying a lowdensity current to the first electroplating solution for a period oftime sufficient to co-deposit the first conductive metal and the metalceramic particles as a first conductive layer on the surface of the atleast one conductive contact region, wherein said low density current isless than 8 amps per square foot (ASF).
 2. The method of claim 1,further comprising, prior to said exposure step, roughening the surfaceof said at least one conductive contact region.
 3. The method of claim1, further comprising, after said supplying step: exposing the circuitpanel to a second electroplating solution comprising a second conductivemetal, and supplying current to the second electroplating solution for aperiod of time sufficient to deposit the second conductive metal as asecond conductive layer on top of the first conductive layer, whereinsaid second conductive metal is selected from the group consisting ofgold, iridium, osmium, palladium, platinum, rhodium, ruthenium, silver,and alloys and combinations thereof.
 4. The method of claim 1, furthercomprising, after said supplying step: exposing the at least oneconductive contact region to a second electroplating solution comprisingthe first conductive metal; and supplying a current to the secondelectroplating solution for a period of time sufficient to induce growthof the first conductive layer.
 5. The method of claim 1, wherein saidfirst electroplating solution is agitated at a rate between 0.5 and 5meters per second during said period of time.
 6. The method of claim 1,wherein the first conductive metal is selected from the group consistingof nickel, silver, copper, gold and alloys of these metals.
 7. Themethod of claim 1, wherein the metal ceramic is a Group IV or Group Vmetal carbide.
 8. The method of claim 7, wherein the metal ceramic istitanium carbide.
 9. The method of claim 8, wherein the first conductivemetal is nickel.
 10. A method for providing asperities on a conductivecontact region of a substrate for forming an electrical connection witha contact location on a semiconductor die, comprising: providing asubstrate having at least one conductive contact region; exposing the atleast one conductive contact region of the substrate to a firstelectroplating solution comprising a first conductive metal and aplurality of metal ceramic particles, wherein the first conductive metalis selected from the group consisting of nickel, silver, copper, gold,and alloys of these metals, and wherein the metal ceramic particles areceramics of a Group IV metal, a Group V metal, or a Group VI metal andwherein the metal ceramic particles have an electrical resistance lessthan about 25 milliohms; and supplying a low density current to thefirst electroplating solution for a period of time sufficient toco-deposit a layer of the first conductive metal and the metal ceramicparticles as a first conductive layer on the surface of the at least oneconductive contact region, wherein said low density current is less than8 amps per square foot and wherein said first electroplating solution isvigorously agitated during said period of time.
 11. The method of claim10, wherein the substrate is an interposer flex panel.
 12. The method ofclaim 10, wherein said agitation is provided by a slurry pump.
 13. Themethod of claim 10, wherein said agitation is provided by air agitation.14. The method of claim 10, wherein said first conductive metal isnickel, and said first electroplating solution further comprises nickelsulfamate.
 15. The method of claim 10, further comprising, after saidsupplying step: exposing the at least one conductive contact region to asecond electroplating solution comprising the first conductive metal;and supplying a current to the second electroplating solution for aperiod of time sufficient to induce growth of the first conductivelayer.
 16. A method for providing asperities on a conductive contactregion of a substrate for forming an electrical connection with acontact location on a semiconductor die, comprising: providing asubstrate having at least one conductive contact region; exposing the atleast one conductive contact region of the substrate to a firstelectroplating solution comprising a first conductive metal and aplurality of metal ceramic particles, wherein the first conductive metalis selected from the group consisting of nickel, silver, copper, gold,and alloys of these metals, and wherein the metal ceramic particles areceramics of a Group IV metal, a Group V metal, or a Group VI metal andwherein the metal ceramic particles have an electrical resistance lessthan about 15 milliohms; supplying a low density current to the firstelectroplating solution for a period of time sufficient to co-deposit alayer of the first conductive metal and the metal ceramic particles as afirst conductive layer on the surface of the at least one conductivecontact region, wherein said low density current is less than 5 amps persquare foot (ASF) and wherein said first electroplating solution isvigorously agitated during said period of time; exposing the at leastone conductive contact region of the substrate to a secondelectroplating solution comprising the first conductive metal; andsupplying a current to the second electroplating solution for a periodof time sufficient to induce growth of the first conductive layer. 17.The method of claim 16, further comprising, after said second supplyingstep: exposing the circuit panel to a third electroplating solutioncomprising a second conductive metal, and supplying current to the thirdelectroplating solution for a period of time sufficient to deposit thesecond conductive metal as a second conductive layer on top of the firstconductive layer, wherein said second conductive metal is selected fromthe group consisting of gold, iridium, osmium, palladium, platinum,rhodium, ruthenium, silver, and alloys and combinations thereof.
 18. Themethod of claim 17, wherein said first conductive metal is nickel orcopper, and said second conductive metal is gold or rhodium.
 19. Themethod of claim 16, wherein said first conductive metal is nickel orcopper, and said metal ceramic is a Group IV or Group V metal carbide.20. The method of claim 19, wherein said metal carbide is titaniumcarbide, vanadium carbide, or hafnium carbide.